Figure 1.

Altered Auxin Levels and Corresponding Gene Expression.

(A) Modulation of auxin levels in the stem. Stem samples were placed in half-strength MS medium for 16 h to deplete their auxin levels, then they were replenished by transfer to the same medium with 20 μM IAA. The graph shows changes in IAA levels at various time points: after 0 h (d0), 4 h (d4), and 16 h (d16) of depletion, and 30 min (i0.5), 2 h (i2), and 4 h (i4) after the addition of IAA. The inset shows a magnification covering the depletion step. n = 3; error bars represent sd. t tests indicated that there were significant differences in auxin levels between d0 and d16 (P = 0.05) and between d16 and both i0.5 and i2 (P ≤ 0.01). FW, fresh weight.

(B) Responses of gene expression in stem tissues to changes in auxin levels. The expression patterns of auxin-responsive genes could be divided into nine clusters. The lines in the graphs represent the average expression profile of all genes in each cluster. The number of auxin-responsive cDNA clones identified by microarray analysis belonging to each cluster is indicated. Supplemental Data Set 1 online provides details of the expression clusters.